The present invention relates to tripod joints. The joints includes an outer joint part, non-rotatingly connected to a first driveshaft, with three circumferentially distributed longitudinally extending tracks to receive rollers. An inner joint part is included which has three radial arms which engage the tracks and on which the rollers are rotatably and radially movably supported. The inner part is non-rotatingly connectable to a second driveshaft. The outer joint part includes an outer annular member directly and firmly connected to the first driveshaft, track elements directly guiding the rollers, and resilient intermediate elements which are arranged between the two and through which torque may be transmitted. The terms of first driveshaft and second driveshaft as used in this context analogously refer to other rotating drive parts such as drive flanges, wheel hubs and the like.
Tripod joints differ from ideal constant velocity universal joints in that, when the joint is in an articulated condition, the transmission of power does not take place in the angle-bisecting plane between the two joint axes. In tripod joints, power transmission takes place in the plane of the tripod arms so that contact takes place in the plane perpendicular to one of the driveshafts.
Nevertheless, even with tripod joints, constant velocity occurs between the first driveshaft and the second driveshaft; the angular speed of the two shafts is always the same. This is achieved as a result of an orbital movement between the outer joint part and inner joint part during rotation of the articulated joint. Apart from other influences, especially friction-loaded rolling movement of the tripod rollers in the tracks of the outer joint part, which influences will not be discussed here in greater detail, the above-mentioned orbital movement also constitutes a negative influencing factor with respect to the NVH behavior (Noise, Vibration, Harshness). This negative influence is particularly pronounced in the case of high-speed shafts and joints. If the shafts are used in vehicles, they adversely affect the driving comfort due to the resulting vibration excitation and noise development.
DE-AS 22 40 436 (U.S. Pat. No. 3,817,057) already proposes joints of the initially mentioned type. Here rubber-elastic material members are provided between the outer annular member and the track elements. It is the purpose of such elements to resiliently dampen rotational impacts in the driveline. However, the problem of an additional vibration excitation resulting from the orbital movement cannot be eliminated in any way by such a measure. On the contrary, this phenomenon very widely occurs with joints of this type as well and leads to the above-mentioned problems which have to be considered separately.
DE-OS 25 30 670, issued Jan. 29, 1976, describes joints where mutual centering means are provided between the outer joint part and the inner joint part. These are designed as ball/cylinder assemblies or ball/calotte assemblies, but the outer joint part is designed in one piece. To ensure functioning in the case of a tripod joint, the contact between the rollers and recesses must be of a resilient nature. This is achieved by lining the recess with an elastomer. Otherwise, without the lining, the joint would not be capable of articulation. Such a design with resilient tracks does not meet the requirements of practical applications.
Finally, DE 19 03 600, proposes a joint with four poles. Here the centering means includes a journal/ball assembly at the outer joint part and a calotte assembly at the inner joint part. In this case, too, the recesses of the outer joint part are directly covered with a resilient material as otherwise the joint would not be capable of articulation. This joint cannot be regarded as meeting the requirements of practical applications either since high torques and high service life values cannot be achieved with such a design.